Despite the name, this is not an authoring editor. It was (perhaps still is) a plug-in converter from Word to SGML and back. In tests conducted for an earlier review, it was able to convert circularly: from Word to SGML, edit the document, convert from SGML back to Word, edit the document, lather, rinse, repeat…losslessly book.
Admittedly it took considerable configuration, but astonishingly, it worked. This was intended to allow a non-SGML person to author a document, have the publications staff convert it and edit it, and then convert back to Word and hand it back to the author to carry on writing or editing, again and again until ready. Microstar’s Near&Far Author for Word provides a similar facility, but embedded within the Word interface itself.